/usr/share/scsh-0.6/env/shadow.scm is in scsh-common-0.6 0.6.7-8.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 | ; Copyright (c) 1993-1999 by Richard Kelsey and Jonathan Rees. See file COPYING.
; Deal with shadowed variables.
; When a variable is shadowed by a variable, split the existing shared
; location into two replacement locations.
; name (structure-ref p name) (define name ...) within a single template
; will lose big.
;(define *replaced-locations* '()) ;alist of (old rep ((uid ...) . new))
(define (shadow-location! old p-uids new replacement)
(if (location-defined? old)
(set-contents! replacement (contents old)))
(set-location-id! old
(vector replacement p-uids new))
(set-location-defined?! old #f)) ;so that exceptions will be raised
(define maybe-replace-location
(let ((memv memv))
(lambda (loc p-uid) ;Package's unique id
(let ((foo (location-id loc)))
(if (vector? foo)
(maybe-replace-location
(if (memv p-uid (vector-ref foo 1))
(vector-ref foo 2)
(vector-ref foo 0))
p-uid)
loc)))))
; Exception handler:
(define (deal-with-replaced-variables succeed)
(lambda (opcode reason loc . rest)
(if (= reason (enum exception undefined-global))
(deal-with-replaced-variable opcode reason loc rest succeed)
(apply signal-exception opcode reason loc rest))))
(define (deal-with-replaced-variable opcode reason loc rest succeed)
(primitive-catch
(lambda (cont)
(let* ((tem (continuation-template cont))
(index (+ (code-vector-ref (template-code tem)
(+ (continuation-pc cont) 2))
(* (code-vector-ref (template-code tem)
(+ (continuation-pc cont) 1))
byte-limit))))
(if (eq? (template-ref tem index) loc)
(let* ((p-uid (do ((env (continuation-env cont)
(vector-ref env 0)))
((not (vector? env)) env)))
(new (maybe-replace-location loc p-uid)))
(if (eq? new loc)
(apply signal-exception opcode reason loc rest)
(begin (template-set! tem index new)
;(signal 'note "Replaced location" loc new p-uid)
(if (location-defined? new)
(succeed new rest)
(apply signal-exception opcode reason new rest)))))
(error "lossage in deal-with-replaced-variables"
loc index))))))
(define-exception-handler (enum op global)
(deal-with-replaced-variables
(lambda (loc more-args)
(contents loc))))
(define-exception-handler (enum op set-global!)
(deal-with-replaced-variables
(lambda (loc more-args)
(set-contents! loc (car more-args)))))
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